Drafting instrument



Patented Jan. 19, 1954 UNITED STATES PATENT oFFIcE" John Arlon Buick,Norfolk, Va. Application August 15, 1951, Serial No. 241,975

'The present invention relates to drafting instruments, and moreparticularly to an instrument for use on drawing boards and the like fordrawing and marking lines at various predetermined angles with respectto a reference edge.

One object is to provide a drafting instrument having a pivoted straightedge provided with an indicator arm which is movable over a protractorscale to indicate the angular position of the pivoted straight edge. Y1' Another object is to provide a draftinginstrument, includingatri-square to which is pivoted a straight edge such that the oppositesides of the .tri-square may be used as a reference edge when the deviceis employed on a drafting board for marking or drawing lines on adrawing.

Another object is to provide a drafting instrument, including a pivotedstraight edge having anindicator arm adjacent the pivot point of saidstraight edge, which is arranged to cooperate with a protractor scale sothat both sides of the straight edge will be unobstructed to permit thedrawing of lines on both sides thereof.

Another object is to provide a drafting instrument having a combinationstraight edge which is pivotally attached to one corner of a tri-square,

and is provided'with locking means for holdingv the straight edge arm ina predetermined angular position with respect to the opposite sides orreference edges of the tri-square.

Another object is to provide a drafting instru- 7' ment having a lockingelement which can be quickly and easily manipulated to lock thecombination straight edge arm in a preselected angular position.

'Another object is to provide a guide strip for maintaining theindicator arm in position on the surface of the tri-square which can "beconveniently employed for lifting the instrument with respect to thedrawing surface by inserting the fingers thereunder so that in theevent'that ink or other drawing fluid is employed, smearing and the likewill not occur. 7

Another object is to provide a locking member for maintaining thestraight edge arm in a pre selected angular position which includescooperating threaded fasteners, which may be formed of a resinousplastic composition having an enlarged head portion at one end tooverlie a relatively large area of the indicator arm adjacent the pivotpoint of said straight edge arm, and thereby securely lock thestraightedge arm in a predetermined position. I

Other objects and advantages of the invention will become apparentduring the course of the 1 Claim." (CI. 33-93) following description ofthe accompanying drawing wherein:

Figure 1 is a plan view of the drafting instru-' ment showing thestraight edge arm in its fully extended position in dotted lines, andits retracted position in full lines. The indicator arm is attached tothe straight edge arm adjacent the pivot thereof, and is shown incooperation with a protractor scale.

Figure 2 is an oblique cross-sectional" view taken on line 2-2 of Figure1, and looking in the direction of the arrows to illustrate theindicator arm and the combination retainer strip therefor and fingergrip.

Figure 3 is an oblique cross-sectional view taken on line 3-3 of Figure1, and looking in the direc- I tion of the arrows to illustrate the armlocking" threaded fastener unit, and'the-manner in which angularposition.

Figure 4 is a fragmentary bottom or rear elevational view, showing themanner in which the straight edge arm is pivo-tally connected to thebase or tri-square, and the manner in which one end thereof is beveledto limit movement of the straight edge arm beyond a angular positionwith respect to one of the reference edges of the base or tri-square,and

Figure 5 is a fragmentary cross-sectional view of a modified form ofstraight edge arm locking means, including separable threaded fastenerelements one of which may be formed of a synthetic resin plasticcomposition similar to the base and pivoted straight edge.

In the drawing, and more in detail there is shown a base memberdesignated 5 which may be formed of transparent clear synthetic resinplastic or Celluloid, and said base is shaped in the form of a 45 angletri-square havingrefen. ence edges 6 and 1 extending at an angle of 90.with respect to one anothenand connected at their outer ends by ahypotenuse edge 8. The right angle corner 9 connects the edges 6 and I,while the opposite corners I 0 and H form included 45 angles. The baseor tri-square 5 is provided with an opening 12 having straight edges !3and I4 parallel with the reference edges 1 and 8 respectively and acurved edge l5. The

straight and curved edges I3-M and I5 are con- The triangular base 5 or45 angl trI square may be placed on a drafting board with either of theopposite reference edges 6 or 1 in registry with a reference line in aconventional manner. Usually, a T-square is employed for this purpose.

Pivotally attached to the corner I of the triangular base is an armwhich is pivotally connected by means of a pivot screw 2| to the base 5,and said pivot screw 2| extends through an opening in the corner I l andsimilarly passes through an opening in the arm 20, so that the threadedend of said pivot screw may receive a correspondingly threaded knurledclamping nut 22. Attached to the underside of the arm 20 is a straightedge arm 23 (Figs. 1 and 4), and said straight edge arm 23 is diagonallycut at the upper and lower portions as at 2* andto form a continuationof the reference edge T and abut the hypotenuse edge 8 respectively. Itis intended to form the pivotedstraight edge arm 23 and arm 20 of asynthetic resin plastic or Celluloid composition similar to the base-5'. such that the draftsman may have clear vision of the drawing onwhich the instrument is used and other delineations thereon. In theevent that the straight edge arm 23 is formed of a synthetic resinplastic composition,- the arm 20 may be joined thereto by a plastic toplastic adhesive, or if desired, the arm 20 ,rnay be integrated with thestraight edge arm 23 in the usual manner;

Formed integral with the arm 20 is an indicator arm- 2} which extends atan angle approximately 45 to the pivoted straight edge arm 23-,. andsaid arm 21 is connected to the arm 20 by an-arcu ate portion 23(Fig. 1) extending along a radius with the pivot screw 2| as its center;The arcuate edge 28 is adapted to be clampingly engaged by; a lockingmember, including-a locking screw 29 having an upper threaded end andahead 30 on the opposite end which is countersunk in an opening in thecorner H spaced from the pivot screw 2| a distance slightly greater thanthe radius of the arcuateedge 28. A-locking knurled thumb nut 3| isprovided'wit'h an internally" threaded opening for receiving thecorrespondingly threaded end 29 of the screw 3E), and said knurled thumbnut 31- is provided with a flanged lowerportion 32 adapted to overliethe arcuate edge; 28 so as to frictionally engage the arm 20 adjacenttheedge' 2'3 and hold the straight edge arm 23 in a preselected angularposition The indicator arm 21 is adapted to cooperate with aprotract'o'r' scale 34, and the end of said arin is'prov ided' with adatum line marlied or otherwise applied to the beveled end edge 33thereof so that it will register with the various degree markings 34 ofthe protractorscaler The protfactor" scale is marked with legends or'nu-Ineral's 31 which read from zero to 4 5- degrees? aifi'dwith' numerals38 reading; in a reverse directiorifrom to 90 degrees; Thus; bothreference edges 6 and 1' may be used by simply' turning the. instrumentabout an angleo'f 45.-

Mounted on the triangular base 5 is a retainer strip!!! which has itsends angularly be'n't'asf; at 4| to provide offset'foot portions 42 Theoffset footportions 42 are riveted or otherwise secured as'at' 43 to thetriangular base 5, and is arranged above the free end of the indicatorarm 21' so as to maintain said arm in position with the beveled end 36projecting or presented to the protractor scale 34. When the draftsinanmayinsert his fingersbeneath the retaining strap 49 to facilitatelifting the instrunent-{ism the drawin'giboai'd; whenit'i's desired to?change the pus'iuqrr thereof.

Iii" the modified forn'i (armament-ita drawing angular lines,

4 in Figure 5, a separable threaded fastener element is shown which canbe substituted for the locking and pivot screws illustrated in the formof the invention shown in Figures 1 to 4 inclusive. In the event thatthe pivot screw 2| and retaining nut 22 is replaced, the separablethreaded fastener shown in Figure 5 may be used both as a pivot screwand locking means. In Fig. 5 the base 51; is the same as before, andincludes a triangular base similar to that shown in Fig. 1. The arm 20ais adapted to be pivotally connected to the base 5a by means of atubular fastener element 50a having a head 5|a which is received intheren larged portion of an opening 52a in the base 5a. The fastenerelement 50a is provided with an internally threaded bore 53a and saidfastener is adapted to extend through an opening 541: in the arm 20asuch that it projects therebeyohd a slight distance. The tubularthreaded fastener 50a may be formed of asyntheticresinplasticcomposition similar to v the base 5a; The tubularthreaded fastener 509i is adapted to receive the externally threadedportion 55a of a retaining screw having an enlarged head portion 56 anda downwardly directed rim portion 51a spaced from the externallythreaded portion 55a by an annular channel 53d. Thus, the arm 20a maybefrictionally and clampingly'f secured to the" base 5a by turning theknurled peripheral portion (not shown) (5r meningestion 51a in adirection to thread the externally threaded portion 55a; in theinternally threaded portion 53a of the cooperating tubular fastener 50a.

If the locking fasftenerfshown in Figure his employed in lieu of thelocking screw and nu-t 29-3| shown in Figs. 1 to 44 inclusive, thedownwardly directed rim portion 51a will engagethe arm 20a and overliethe areuate' edge" thereof to lock the arm in a pre-selected positionwhen the head 56a is turned in a right directioni The cooperatingfastener element 560/ shown mm; 5, may likewise be formed of a"synthetic resin plastic of a color '11 contrast to the base" and pivotedstraight edge arm as well as the indicator arm;

It" will thus be' Senjthat the straight edge arm 23in Figs. 1 to 4hasits o pcsedeu es in parallel relation one with the other, and withthe hypotenuse edge 8 when the instrument is in its retracted position.When in this position, 45 degree lines may be drawn insubstantially thesame manner as a tri-square is employed-by placing the reference edgesreference line or surface on the drawing board.

When it is desired to draw lines from zero td 45 degrees; the" referenceedge 1 is placed against a horizontal or longitudinal referencesurface'i Similarly, by

ii against horizontal reference surface, angles froiri 45 to degrees maybed'rawn". Obviously, the'-triangularbase 5 or tri-s'duare can beplacedm otherpositions so that the straight edge arm 23 can be adjusted tovarious predetermined angular positions and held therein by the lookingfastener elements 29-3|' shown" in Figs. 1 to -inclusi've, and Eta-55dshown in Fig. 5i-

It is to be understood, that the forms of the invention herewith shownand described areto be takenas preferred embodiments thereof, and thatvarious changes in the shape, size and arrangement of parts may beresorted" to without departing from the s pirit ofthe invention or thescope of the subjoined claim.

In a drafting instrument, a trianguier" base 6 and I against a placingthe reference edge-- straight edge arm having one end pivotally con-'nected to a corner of said triangular base at a point in the anglebetween the hypotenuse and base and near the intersection thereof, anindicator arm integrally connected to said straight edge arm adjacentthe pivoted end thereof and projecting over the base to cooperate with aprotractor scale thereon, a guide' strap having its ends afiixed to saidtriangular base adjacent the ends of said scale to guide said indicatorarm in close proximity to the graduations of said scale, an arcuateportion connecting said straight edge arm and said indicator arm, therim of the are extending along a radius having the common pivot of thestraight edge arm and the indicator arm as its center, said arcuate rimlying in close proximity to said center, and a threaded fastener for illholding said straight edge and indicator arms 20 in a position ofangular adjustment, said threaded fastener being arranged on the basebetween said arms with a rim of the fastener overlying and frictionallyengaging said arcuate rim.

JOHN ARLON BUICK.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,365,779 Grave June 18, 1921 1,755,152 Parker Apr. 15, 19302,104,354 Rich Jan. 4, 1938 2,154,753 Kallio Apr. 18, 1939 FOREIGNPATENTS Number Country Date 2,813 Great Britain Feb. 5, 1907 355,856Great Britain Sept. 3, 1931 548,282 Great Britain Oct. 1, 1942

